1. Field of the Invention
The invention relates to a process and to a device for executing the process for calibrating throttle bores, particularly throttle bores in injection valves for internal combustion engines.
2. Description of the Prior Art
It is known for throttle bores of the type in question to be hydroerosively machined by means of suspensions, e.g. comprised of a mineral oil of suitable viscosity containing abrasive grit, and in this connection, for the throttle bores to be calibrated to the through flow desired in the (subsequent) operation of the relevant work piece (so-called HE process). Since the machining pressure of the fluid at the outlet of the throttle bore decreases, cavitation occurs in the fluid, which leads to an undesirable dispersion of the cavitation-free through flow of the throttle bore.
The object of the invention is to improve the calibration of throttle bores so that a reduction of the dispersion of the cavitation-free through flow is produced.
According to the invention, the object is obtained with a process of the generic type described above and with a device for executing this process by producing a counterpressure at the outflow side of the throttle bore to thereby prevent cavitation of the fluid.
The invention permits a cavitation-free calibration of the throttle bore, since the counterpressure on the outflow side correspondingly reduces the pressure drop and as a result hinders the formation of gas bubbles in the machining fluid. Otherwise, the erosive abrasion machining of the throttle bore can take place in the usual way (e.g. in accordance with the HE process).
The process according to the invention consequently permits the dispersion of the cavitation-free through flow to be reduced from the previous xc2x13% to approx. xc2x10.6% in comparison to other pre-machining processes (e.g. drilling or erosion).